1. Field of the Invention
The present invention relates to formation of one or more barrier layers and, more particularly, to one or more barrier layers formed using chemisorption techniques.
2. Description of the Related Art
In manufacturing integrated circuits, one or more barrier layers are often used to inhibit diffusion of one or more materials in metal layers, as well as other impurities from intermediate dielectric layers, into elements underlying such barrier layers, such as transistor gates, capacitor dielectrics, transistor wells, transistor channels, electrical barrier regions, interconnects, among other known elements of integrated circuits.
Though a barrier layer may limit to prevent migration of unwanted materials into such elements, its introduction creates an interface at least in part between itself and one or more metal layers. For sub half-micron (0.5 μm) semiconductor devices, microscopic reaction at an interface between metal and barrier layers can cause degradation of integrated circuits, including but not limited to increased electrical resistance of such metal layers. Accordingly, though barrier layers have become a component for improving reliability of interconnect metallization schemes, it is desirable to mitigate “side effects” caused by introduction of such barrier layers.
Compounds of refractory metals such as, for example, nitrides, borides, and carbides are targets as diffusion barriers because of their chemical inertness and low resistivities (e.g., sheet resistivities typically less than about 200 μΩ-cm). In particular, borides such as, including but not limited to titanium diboride (TiB2), have been used as a barrier material owing to their low sheet resistivities (e.g., resistivities less than about 150 μΩ-cm).
Boride barrier layers are conventionally formed using chemical vapor deposition (CVD) techniques. For example, titanium tetrachloride (TiCl4) may be reacted with diborane (B2H6) to form titanium diboride (TiB2) using CVD. However, when Cl-based chemistries are used to form boride barrier layers, reliability problems can occur. In particular, boride layers formed using CVD chlorine-based chemistries typically have a relatively high chlorine (Cl) content, namely, chlorine content greater than about 3 percent. A high chlorine content is undesirable because migrating chlorine from a boride barrier layer into adjacent interconnection layer may increase contact resistance of such interconnection layer and potentially change one or more characteristics of integrated circuits made therewith.
Therefore, a need exists for barrier layers for integrated circuit fabrication with little to no side effects owing to their introduction. Particularly desirable would be a barrier layer useful for interconnect structures.